In recent years, a medical diagnostic imaging apparatus including a plurality of medical diagnostic imaging apparatuses integrated with each other has been in practical use. Specifically, an apparatus including a PET (Positron Emission Tomography) diagnostic apparatus for functional diagnosis of body tissue of a subject, and an X-ray CT (Computed Tomography) apparatus for imaging morphological information of body tissue of a subject integrated with each other (also referred to as a PET-CT apparatus) has been in practical use.
The PET-CT apparatus can continuously conduct a PET examination and an X-ray CT examination. Thus, the PET-CT apparatus can, by itself, generate a PET image and an X-ray CT image to generate a fusion image of the PET image and the X-ray CT image superimposed on each other.
In such a medical diagnostic imaging apparatus, generally, a PET gantry (radiation detection unit) used in the PET diagnostic apparatus, and an X-ray CT gantry (X-ray scanning unit) used in the X-ray CT apparatus are placed close to each other. Such a medical diagnostic imaging apparatus includes a bed having a top panel on which a human subject is placed, and the PET diagnostic apparatus and the X-ray CT apparatus share the bed.
In the medical diagnostic imaging apparatus, the PET gantry in the PET diagnostic apparatus and the X-ray CT gantry in the X-ray CT apparatus are successively arranged in a tandem positional relationship, and the PET gantry and the X-ray CT gantry each have a tunnel portion extending therethrough. The top panel of the bed is inserted into the tunnel portions in the gantries longitudinally of the top panel.
Thus, in the medical diagnostic imaging apparatus, a distance between the bed and the radiation detection unit of the PET diagnostic apparatus is different from a distance between the bed and the X-ray scanning unit of the X-ray CT apparatus, and thus depression of the top panel (also referred to as bending of the top panel) also differs due to a load in an imaging position of each gantry. Thus, various methods for correcting the bending of the top panel have been studied.
In a medical diagnostic imaging apparatus using a plurality of imaging methods, imaging is performed by each imaging method, and thus imaging surfaces shows different positions (imaging positions), and the top panel bends in a different manner in each imaging position. Specifically, even if the PET gantry and the X-ray CT gantry image the same site, bending of the top panel due to a load is different. For the PET diagnostic apparatus, a position of the top panel is not projected on a PET image, and thus when the PET image and the X-ray CT image are superimposed on each other, it is difficult to align the positions of the top panels in the captured images, thereby making it difficult to generate a fusion image with high accuracy of the PET image and the X-ray CT image properly superimposed on each other.